Tuberculosis, 2000

While the number of
tuberculosis (TB) cases reported nationally has been declining since 1993,
the incidence and epidemiology of TB in Minnesota are following different
trends. In 2000, 178 new cases of TB disease (3.6 per 100,000 population)
were reported. This is the second largest number of cases reported in
20 years, after the 201 cases reported in 1999. For the fourth consecutive
year, the incidence of TB disease in Minnesota remains at or above the
national goal of 3.5 cases per 100,000 for the year 2000.

During 2000, 25 of the 87 counties in Minnesota reported at least one
case of TB disease. However, the majority (76%) of TB cases occurred in
the seven-county Twin Cities metropolitan area, particularly among residents
of Hennepin (9.4 per 100,000) and Ramsey (4.7 per 100,000) Counties. Approximately
20% of cases occurred in greater Minnesota, with increasing incidence
in specific areas.

The most significant factor in the epidemiology of TB in Minnesota is
the large and increasing percentage of TB cases that occur among foreign-born
persons (Figure 9). The percentage continued to increase in 2000, with
146 (82%) cases occurring in this population. This trend reflects the
changing demographics of immigrant populations arriving in the state,
particularly persons arriving from regions of the world where TB is prevalent.
Among the 146 foreign-born persons diagnosed with TB disease in Minnesota
during 2000, 41 (28%) were diagnosed within 12 months of arrival in the
United States; an additional 30 (21%) were diagnosed 2 to 5 years after
arriving in this country. The most common regions of origin for foreign-born
persons with TB disease reported in 2000 included sub-Saharan Africa (58%),
South/Southeast Asia (22%), and Latin American/Caribbean countries (18%)
(Figure 10). More than half of foreign-born TB cases were 20 to 39 years
of age, while the most common (28%) age group among U.S.-born cases was
those 60 years of age or older. Foreign-born TB cases were more likely
than those born in the U.S. to have extra-pulmonary sites of disease (42%
vs. 33%, respectively). Other less frequent risk factors among TB cases
in Minnesota included HIV infection (4%), homelessness (3%), incarceration
in a correctional facility (2%), and residence in a nursing home (2%).

The increasing incidence of drug-resistant TB is a critical public health
and clinical concern globally. In 2000, Minnesota reported 37 (26%) cases
of drug-resistant TB among the 140 culture-confirmed cases for whom drug
susceptibility results were available, including 23 (16%) cases resistant
to isoniazid and one (1%) case of multi-drug resistant (MDR) disease resistant
to isoniazid, rifampin, pyrazinamide, and streptomycin. Compared to data
from the past 5 years, these figures represent an increase in both overall
drug resistance and INH-resistance. However, the specific drug which showed
the largest increase in resistance was streptomycin (17% of cases were
resistant), which is the least commonly used of the five first-line anti-TB
medications. Foreign-born TB patients in Minnesota are approximately three
times more likely than those born in the U.S. to have drug-resistant disease
(Table 6). Of 37 persons with drug-resistant TB disease reported in 2000,
34 (92%) were born outside the U.S., including the case of MDR-TB. These
cases likely represented primary drug resistance acquired overseas rather
than secondary resistance resulting from nonadherence to prescribed therapy.
Current national guidelines recommend initial four-drug therapy for all
TB cases in areas where the prevalence of INH resistance is 4% or greater.
Twelve percent of all TB cases reported in Minnesota from 1996 to 2000
were resistant to at least INH; therefore, all TB cases in Minnesota initially
should receive four-drug therapy until drug sensitivities are known.

More detailed TB surveillance data and other TB-related resources are
available on the MDH TB web site.